In recent years, for example, the diameter of semiconductor wafers (hereinafter, referred to as “wafers”) are increasing. In addition, there is a desire to make the wafers thin in a specified process such as mounting or the like. However, a large-diameter thin wafer is likely to be bent or cracked if the wafer is transferred or polished as is. Therefore, in order to reinforce the wafer, the wafer is bonded to, for example, a wafer or a glass substrate that acts as a support substrate. Thereafter, a predetermined process such as a polishing process is performed on the wafer in a state where the wafer is bonded to the support substrate as described above, and subsequently, the wafer and the support substrate are peeled off from each other.
Such a peeling is performed, for example, using a peeling device. For example, the peeling device includes a first holder for holding the wafer, a second holder for holding the support substrate, and a nozzle for injecting liquid between the wafer and the support substrate. In the peeling device, the nozzle injects liquid between the wafer and the support substrate which are bonded together at an injection pressure. The injection pressure is greater than a bonding strength applied in bonding the wafer and the support substrate, preferably, at an injection pressure that is two or more times stronger than the bonding strength, thus peeling the wafer and the support substrate (see Patent Document 1).